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Very low frequency

About: Very low frequency is a research topic. Over the lifetime, 1540 publications have been published within this topic receiving 24233 citations. The topic is also known as: VLF.


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Journal ArticleDOI
TL;DR: In this paper, the authors present evidence for a relaxation phenomenon in the generation of discrete very-low-frequency (VLF) emissions, and a qualitative explanation of the stability of symmetrical three-phase emission is given.
Abstract: : When periodic very-low-frequency (VLF) emissions of more than one set are observed concurrently (multiphase emissions) the observation of three sets symmetrically spaced is surprisingly frequent. Evidence is presented which suggests that two sets represent a transient situation, and that the strength of one emission may depend on the strength of, and the elasped time since the preceding emission. The data are interpreted as evidence of a relaxation phenomenon in the generation of discrete VLF emissions, and a qualitative explanation of the stability of symmetrical three-phase emission is given. (Author)

10 citations

Journal ArticleDOI
TL;DR: In this article, the authors explore the possibility that early Trimpi events result from lighting-generated, electric field impulses lowering the mirror altitudes of trapped electrons, and show that to overcome the mirror force on energetic electrons, upward-directed electric fields with strengths of a few tens of mV/m are required.

10 citations

Journal ArticleDOI
TL;DR: In this article, a mode theory computer model for propagation of VLF waves in the Antarctic Earth-ionosphere waveguide is used to illustrate the characteristics of 3.79-kHz signals as they propagate from Siple toward the receivers at Halley and South Pole stations.
Abstract: The burst precipitation of energetic electrons (≥40 keV), induced by interactions with lightning-generated whistler mode waves, has been observed to cause phase and amplitude perturbations on subionospheric VLF signals (“Trimpi” events). With a knowledge of the propagation characteristics of the subionospheric signal, analysis of the perturbation details can lead to estimates of the energy, extent, and location of the precipitation. Trimpi events have been observed on VLF signals propagating at high latitudes (L ≥ 4) over Antarctica, on 3.79-kHz signals transmitted from the horizontal dipole at Siple station. A mode theory computer model for propagation of VLF waves in the Antarctic Earth-ionosphere waveguide is used to illustrate the characteristics of 3.79-kHz signals as they propagate from Siple toward VLF receivers at Halley and South Pole stations. To simulate the effects of precipitation, localized depressions in the ionospheric reflection height are introduced over the great circle propagation paths in the model, and it is seen that, while the amplitude and phase perturbations of some specific events are accurately reproduced, large positive amplitude (up to 6 dB) Trimpi events at Halley cannot be reproduced. Calculations are presented which show that signals echoing from precipitation patches located away from the great circle path could be the cause of such signatures.

10 citations

Journal ArticleDOI
TL;DR: In this paper, the diurnal variations of the phase and amplitude of VLF waves on a frequency of 13.6 kHz propagated over the west-to-east transequatorial path from La Reunion to Inubo, Japan, are analyzed.

10 citations

Journal ArticleDOI
TL;DR: In this article, the authors used data from the low-inclination Communication/Navigation Outage Forecast System satellite to test this semi-quantitatively, for broadband Very Low Frequency emissions from lightning.
Abstract: Both ray theory and full-wave models of Very Low Frequency transmission through the ionospheric D-layer predict that the transmission is greatly suppressed near the geomagnetic equator. We use data from the low-inclination Communication/Navigation Outage Forecast System satellite to test this semi-quantitatively, for broadband Very Low Frequency emissions from lightning. Approximate ground-truthing of the incident wavefields in the Earth Ionosphere Waveguide is provided by the World Wide Lightning Location Network. Observations of the wavefields at the satellite are provided by the Vector Electric Field Instrument aboard the satellite. The data set comprises whistler observations with the satellite at magnetic latitudes < 26 deg. Thus our conclusions, too, must be limited to the near-equatorial region, and are not necessarily predictive of mid-latitude whistler properties. We find that in most broadband recordings of radio waves at the satellite, very few of the lightning strokes result in a detectable radio pulse at the satellite. However, in a minority of the recordings, there is enhanced transmission of Very Low Frequency lightning emissions through the D-layer, at a level exceeding model predictions by at least an order-of-magnitude. We show that kilometric-scale D-layer irregularities may be implicated in the enhanced transmission. This observation of sporadic enhancements at low magnetic latitude, made with broadband lightning emissions, is consistent with an earlier review of D-layer transmission for transmission from powerful man-made radio beacons.

10 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202320
202232
202156
202048
201942
201852